Arrangement in connection with a patient circuit and an absorber means. The arrangement comprises an information transfer means and an electronic means and a transponder electronically programmed with desired information. The transponder is attached to the absorber means. The information transfer means is arranged to communicate with the transponder, and the electronic means is arranged to carry out desired procedures from the basis of the information obtained from the anaesthesia/ventilation system and via the information transfer means from the transponder attached to the absorber means.